1. Field of the Invention
The present invention relates to a multimedia data decoding apparatus and method, and more particularly, to a multimedia data decoding apparatus and method managing a memory buffer that temporarily stores multimedia data to decode the multimedia data in an MPEG-4 format.
2. Description of the Related Art
The Moving Picture Expert Group (MPEG) is a name of a family of standards used for compressing and decompressing motion pictures (established in 1988). Unlike Joint Photographic Experts Group (JPEG) that defines a compression of a still picture, the MPEG defines the standards used for compressing and coding a multimedia data, like audio/video data, that continuously varies over time, for a purpose of data transmission.
Presently, MPEG-1, MPEG-2, MPEG-3 and MPEG-4 are available as the MPEG. The MPEG-1 provides digital recording media like CD-ROM, with image and sound quality like that of a Video Cassette Recorder (VCR). The MPEG-2 is an improvement from the MPEG-1 in terms of an audio/video compressing efficiency that provides the image and sound quality of the high resolution digital video apparatus, such as digital TVs, interactive TVs, DVDs. The MPEG-3 is a further improvement from the MPEG-2,. The MPEG-3 is an improved video compression technology, which is aimed to obtain a same high-resolution picture as that of HDTV. As MPEG-3 is now part of the MPEG-2, there is officially no MPEG-3 in the MPEG. The MPEG-4 is a video compression technology developed for a next generation bi-directional multimedia communication such as the Internet, digital TV, DVD, mobile communications. The MPEG-4 is the standard to code the multimedia data for all types of broadcasting, the Internet, movies, mobile communications, and games, and provides transmission functions like interactivity of a computer and transmission of communication altogether.
FIG. 1 is a block diagram schematically showing a conventional multimedia data decoding apparatus applied to MPEG-4. As shown in FIG. 1, the conventional multimedia decoding apparatus includes a multi-switching unit 13 that divides data from received multimedia data according to respective types of data, an input buffering unit 14 that stores the multimedia data output from the multi-switching unit 13 for a predetermined time, and a decoding unit 15 that decodes the multimedia data output from the input buffering unit 14 into an original signal. The conventional multimedia decoding apparatus further includes an output buffering unit 17 that stores the multimedia data output decoded by the decoding unit 15 for a predetermined time, and a compositor 18 that calculates a display position of the decoded multimedia data output from the output buffering unit 17 on a screen. The conventional multimedia data decoding apparatus has a control unit 11 that controls the operation of the multi-switching unit 13, the input buffering unit 14, the decoding unit 15, the output buffering unit 17, and the compositor 18, and sets sizes of buffers 14a, 14b, 14c, 17a, 17b, 17c of the input buffering unit 14 and the output buffering unit 17, respectively.
The conventional multimedia data decoding apparatus receives continuous streams of multimedia data, which are rich media, and performs decoding and outputting. When the multimedia data is input to the buffers 14a, 14b, 14c of the input buffering unit 14, decoders 15a, 15b, 15c of the decoding unit 15 decode the data into the original signal. The buffers 17a, 17b, 17c of the output buffering unit 17 store the decoded data, and output the data to the compositor 18 according to the command from the control unit 11.
The input buffering unit 14 and the output buffering unit 17 of the multimedia data decoding apparatus are, however, set to have a predetermined capacity regardless of amounts of streams of different types of multimedia data. Accordingly, the control unit 11 has to control the buffering operation of the input buffering unit 14 and the output buffering unit 17 in consideration of the amounts of multimedia data streams.
However, if a proper number of buffers of proper amounts are employed in the multimedia data decoding apparatus to solve the above-mentioned problem, another problem of capacity waste arises when the data is received in different amounts. Another problem of increased product costs to produce the multimedia data decoding apparatus with sufficient buffers with sufficient capacity also exists.